Rice Rocket..

After reading some posts alot seems to do with the MAF sesor and was wondering how you can tell it s agoner.

Thanks

Ricey

Absolute Shower

I wonder if mine is faulty too. I've got Secs and it has readings that vary even when the injection pulse is constant...at idle, the air flow varies but not by much. I find an ECU reset will make the car hickup on almost no throttle at times for about 50 mile.

ozzy

SECS should tell you for sure as you can monitor the voltage from the MAF sensor itself.

Another method is using an Air/Fuel ratio meter. When the MAF starts failing it should make the car run leaner and a AFR would give you warning of this.

AFAIK the only ways are:-

1. Monitor voltage via ECU (SECS, DeltaDash, Select Monitor)
2. Monitor voltage directly (multimeter)
3. Indication of lean running via AFR meter (backed up with Knocklink to show if car is detting)
4. Pay £75 for a new one and hope it cures things

Personally, I think it should be possible to build a simple bit of electronics that could plug into the MAF wiring and display/log the voltages. That would be a simpler (and cheaper) method of monitoring the MAF.

SECS and DeltaDash are the better choices since it gives you more data to back-up the case for a faulty MAF, but they're a bit expensive unless you have a lot of engine mods and need to monitor things regularly.

Ideally you'd want a friendly dealer to give you a MAF on a sale or return basis.

Stefan

Absolute Shower

Stefan...what would the secs read with slightly faulty MAF? The AF g/s reads do vary but not by lots...not sure if this correct with injector pulse being constant.

ALi-B

iTrader: (1)

It's very difficult to tell. A MAF sensor doesn't just "Fail" they degrade over a period of time and loose their linerarity...i.e they may be fine at low revs, but read incorrectly at high revs.

It's only when they degrade to the extent that it affects low speed running and/or idle (noticable after reset) that they become noticiable. Or they completely fail and you get the Check Engine Light.

Also to complicate things, symptons that are caused by other things such as bad ignition components, o/s sensors, knock sensors, clogged injectors can be mistaken as a MAF failure or vica versa. A knocklink and/or AFR metre is always a good first indentification that something is not right.
That is why I am very cynical of people giving one line answers to people who post on here about bad engine running and say "sounds like MAF mate" The best way is to take it to a specialist who has the experiance and knows what they are doing.

Alternatively, I was working on an idea of doing something simlar to "Dynomite Scoobies" and try and get people to post in details of typical voltage/resistance readings of good MAF sensors at specific no-load RPM's for each model year and variant. Then if someone is suspicious of a duff MAF sensor it could be looked up on a table and compared. Unfortuantely the hitch with the idea it's very difficult as readings vary with air temperature so the inconsistancies would be too great

[Edited by ALi-B - 12/29/2003 3:02:47 PM]

ozzy

AS,

Sorry, I've no idea m8 Best idea is to post a seperate topic asking what the MAF voltages should be. One of the experienced mappers should be able to provide details on the correct values.

As Ali-B says, it's not so simple. They don't always just fail, but degrade over time. I still feel the degredation can be logged, but the voltages would need to be monitored and logged over a period of time and the effects monitored via AFR and Knocklink meters.

I'm with Ali-B and hate the one-line answers. It's true MAF's are a common fault, but I certainly wouldn't go out and blindly pay £75 for a new sensor that may (or may not) cure the problem unless I understand exactly what's going on.

A duff MAF affects fuelling, making it run lean and increasing the risk of det (which leads to broken engines). If you monitor AFR and knock, then it should give an indication if the MAF is working or not.

Stefan

Absolute Shower

Cheers bloke. The only reason I wonder is when the ECU is reset and the 1st 50/100 miles added. Can run funny, but like you said, that can be slightly faulty MAF.

I'll add topic for SECs and see what others get.